1. Field of the Invention
This invention relates to an apparatus and method for drawing continuous metallic fiber and more particularly to an apparatus and a method for heating and drawing wire for providing a drawn metallic fiber.
2. Description of the Related Art
The art of metal working and metal forming have been well known for a great number of years. Metal may be deformed into various useful shapes by a multitude of apparatuses and methods. One particular form of metal working comprises the working and/or fashioning of metallic wire into fine metallic wire.
Metallic wires and more particularly fine metallic wires have found a wide variety of applications in modern military, industrial and consumer applications. Of the many processes of metal working that have been developed by the prior art, the process of wire drawing is considered one of the preferred processes to produce fine metallic wires. The process of wire drawing has proven to be an effective technique to reduce the diameter of metallic wire. A commercially feasible conventional wire drawing process is capable of producing metallic wire having a diameter of only 100 microns.
In a conventional wire drawing process, a metallic wire is passed through a wire drawing die for reducing the diameter of the metallic wire. In many cases, the metallic wire is passed through a series of wire drawing dies for producing the fine metallic wires. Unfortunately, the production of fine metallic wires by a wire drawing process remains a costly undertaking. In addition, the fine metallic wires may be contaminated by wire drawing dies during the conventional wire drawing process.
The drawing of ductile metallic wire may be accomplished by other drawing processes. One example of a non-conventional wire drawing process comprises the use of a laser to heat the ductile metallic wire. Laser radiation can be focused using a lens system to produce a small spot of high intensity heat energy. The high intensity heat energy may be used for drawing the ductile metallic wire in a non-conventional fashion. The following United States patents are representative of the uses of lasers for heating ductile metallic wire. Many of these United States patents employ complex systems to modify the shape of the laser beam to produce desired heating effects for the production of small diameter wires.
U.S. Pat. No. 3,944,640 to Haggerty et al teaches the method of forming fibers of refractory materials using a focused laser beam and optical system to create a heating zone. The laser beam is split into four beams focused on the refractory material.
U.S. Pat. No. 5,336,360 and U.S. Pat. No. 5,549,971 to Nordine teaches laser assisted fiber growth which includes small diameter fibers of zinc or tungsten of 10 to 170 micrometers. The fiber growth is achieved by movement of a metallurgical microscope stage. The laser beam has a focal point adjusted to coincide with the tip of the growing fiber. Producing an annular laser beam aligned with the axis of the fiber has proved to be an effective though more complex method to control laser energy.
U.S. Pat. No. 3,865,564 to Jaeger et al teaches the drawing of both clad and unclad glass fibers from preform using a laser beam having an annular cross section to soften the preform. The annular laser beam is directed along the axis of the fiber. A modulated control system is also discussed.
U.S. Pat. No. 3,981,705 to Jaeger et al teaches the use of a conical reflector to focus laser radiation in an annular configuration around a glass preform in drawing glass fibers.
U.S. Pat. No. 3,943,324 to Haggerty discloses an apparatus for forming refractory tubing that includes creating a heated zone using a laser. Various optical systems are illustrated for beam splitting and creating annular laser beam configuration.
U.S. Pat. No. 4,135,902 to Oehrle teaches the use of an annular beam to form a melt zone on a fiber using an optical system which includes oscillating galvanometer controlled mirrors, fixed mirror, and a conical reflector to focus the annular laser beam at the surface of the fiber.
U.S. Pat. No. 4,215,263 to Grey et al teaches the use of a rotating reflector, annular mirrors and a conical reflector to create an annular laser beam heating zone for drawing an optical wave guide wherein the annular laser beam does not intersect the axis of the blank wave guide.
U.S. Pat. No. 4,383,843 to Iyengar suggests use of an annular laser beam as a source for heating a preform from which a light guide fiber is drawn.
U.S. Pat. No. 4,547,650 to Arditty et al discloses an optical system utilizing a laser beam directed towards a spherical mirror then from an ellipsoidal mirror to direct the laser energy in a threadlike annular heating zone.
Although the aforementioned prior art provided a method of fine wire production, these prior art processes did have a major disadvantage and did not fulfill the needs of the wire drawing art.
Therefore, it is an object of the present invention to provide an apparatus and method for drawing continuous metallic fiber that overcomes the disadvantages of the prior art devices and provides a substantial contribution to the wire and metallic fiber production art.
Another object of this invention is to provide an apparatus and method for drawing continuous metallic fiber without the introduction of contaminants into the drawn continuous metallic fiber.
Another object of this invention is to provide an apparatus and method for drawing continuous metallic fiber and capable of accurately producing fine metallic fiber in commercial quantities.
Another object of this invention is to provide an apparatus and method for drawing continuous metallic fiber that is reliable and energy efficient.
Another object of this invention is to provide an apparatus and method for drawing continuous metallic fiber with reduced production costs over the prior art techniques and devices.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment of the invention.
A specific embodiment of the present invention is shown in the attached drawings. For the purpose of summarizing the invention, the invention relates to an apparatus for drawing a wire having a first diameter to provide a metallic fiber having a reduced second diameter comprising a feed mechanism for moving the wire at a first linear velocity. A laser beam heats a region of the wire and a draw mechanism draws the heated wire at a second linear velocity for providing a metallic fiber having a second diameter.
In a more specific of the invention, the laser beam heats the region of the wire to a visco-elastic temperature. The second linear velocity is greater than the first linear velocity. The feed and the draw mechanisms comprise a feed capstan drive and a draw capstan drive, respectively. The laser beam may comprise a beam splitter for dividing the laser output beam into a first laser beam and a second laser beam for impinging upon a first and a second side of the wire.
A chamber has an entry groove and an exit groove with the wire entering the chamber through the entry groove and with the drawn metallic fiber exiting the chamber through the exit groove. The chamber has a fluid inlet port for receiving a pressurized fluid atmosphere for enveloping the wire. The pressurized fluid atmosphere exits the entry groove and the exit groove for providing a fluid bearing for the wire within the entry groove and for providing a fluid bearing for the drawn metallic fiber within the exit groove. The pressurized fluid atmosphere exits the exit groove for cooling the drawn metallic fiber emanating from the heated region. The chamber has a window substantially transparent to the laser beam for heating the region of the wire within the chamber.
A first and a second sensor sense the first diameter of the wire and the second diameter of the metallic fiber, respectively. A control module is connected to the first and second sensors for controlling the first linear velocity and the second linear velocity for controlling the reduction of the second diameter from the first diameter.
The invention is also incorporated into the method of drawing a wire having a first diameter to a metallic fiber having a second diameter comprising the steps of feeding the wire at a first linear velocity. The wire is heated to a visco-elastic temperature region with a laser. The wire is drawn at second linear velocity to produce the metallic fiber having a reduced second diameter.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject matter of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention.